The present invention relates to an armchair adapted to take variable positions due to the thrust action exerted on the seat and the backrest by the sitting person so as to follow the movements of said person.
Several types of chairs or armchairs are available on the market, in which the variable position is obtained by the static adjustments provided, as well as by the dynamic features of the peculiar elastic deformability of the seat or back structure or elastic means interposed between the structural elements of the chair.
Pressure exerted by the sitting person on the seat or the backrest or on both elements at the same time, modifies the chair position adjusting the position as far as possible to the new sitting position.
However, more particularly in the frequent changes from the sitting position crouching forward to the stretched position backward, the user feel the resistance of the chair structure to follow said movements. More particularly the user feels the annoying scraping against the surface of the seat or the backrest with consequent trouble and inconvenience.
Moreover the most natural positions the user aims to take, are often constrained only to the intrinsic elastic deformability of the seat and backrest padding without any actual possibility of adjustment when the user is sitting.
In order to remove said drawbacks, the international application of the same inventor published as document WO00/18274, discloses a chair with variable position allowing the sitting position to change from a sitting position crouching forward to another sitting position generally stretched backward. This is obtained merely exerting a thrust on the seat that changes its position relative to the chair support without scraping of the person sitting on the seat surface. Moreover the amount of position variation may be modified by acting on proper adjustment members.
The chair with variable position disclosed in said document has however the drawback to allow only straight seat movements back and forth along a plane. Another drawback consists in that seat and backrest are connected to each other, leading to an undesired constraint because a movement of the seat causes anyway a certain movement of the backrest.
In other words the movements of seat and backrest are interdependent and cannot be separated.
The U.S. Pat. No. 6,116,687 discloses a functional chair having a seat part connected to the head part of the pedestal via a joint comprising an elastomeric material which permits the tilting of the seat part.
The U.S. Pat. No. 4,640,548 discloses an adjustable chair having three horizontal transvers axes connecting the seat and the column, the column and the curved supporting bar and the curved supporting bar and the seat, respectively.
At least one axis permits both the swiveling motion and the relative shift.
The U.S. Pat. No. 4,986,601 discloses a tilting mechanism for a seat able to tilt the seat both forward and backward. The supporting member on which the backrest is mounted is connected with this seat plate so that the supporting member acts interlockingly with that one of the seat plate.
The present invention aims at overcoming this limitation.
More particularly the object of the present invention is to provide a chair or armchair with variable position allowing a greater number of degrees of freedom in the movements of both the seat and the backrest.
Another object is to provide a chair in which seat and backrest can be moved independently from one another when desired.
A last but not least object is to provide a chair allowing movements of both seat and backrest forward, backward, laterally and even on planes other then the original rest ones.
Said objects are attained by an armchair with variable position the main features of which are according to claim 1.
According to a preferred embodiment the support structure consists of a plurality of radially arranged bearing elements connected to the lower end of the support post.
Advantageously in view of the combination of the mutual sliding motion between seat and backrest and of the degree of freedom given by the elastic means to both seat and backrest, the rotary translatory movement of the seat is generated also on other planes than the initial resting plane and a movement of the backrest which is substantially independent from the movement of the seat, so that the user""s back is always leaning on the backrest even when changing his rest position on the seat, for instance in case of changing crossing of the legs.